by Gau, Robert J., Case, Ray, Penner, David F., McLoughlin, Philip D.
Published in Arctic (01.12.2002)

by Kennedy, A.J, Penner, D.F, Green, J.E
Published in Forestry chronicle (01.08.1989)

by Wilkinson, P.F, Shank, C.C, Penner, D.F
Published in The Journal of wildlife management (1976)